Peptide Aldehyde Synthesis and Purification

[puri]

I am interested in the following peptide N-carbobenzoyl-Ile-Glu-(OtBu)-Ala-Leu-CHO. It isnt too difficult to synthesize, however, the purification is the difficult part. 90% can be done but when trying to go above that (the target is 95%), the purity drops. It is very prone to racemization as well.

We used 0.1% TFA in 100% acetonitrile and 0.1% TFA in 100% water to purify the peptide, and methanol. Is there a better process or some sort of special technology we're missing here? Does anyone have the complete purification procedure from start to finish?

[oBWhat]

Hey Puri! welcome to the forums!

thats interesting peptide to make...

There are many techniques out there that could probably work well for you:

have you looked into HPLC methods for peptide purification?

A really great Peptide Purification Article here
http://www.polymerlabs.com/pdfs/specchem.pdf



Reverse Phase Chromatography
http://www.ionexchanger.com/Pharmace...tein_purif.htm

Ion Exchange HPLC
http://www.ncbi.nlm.nih.gov/entrez/q...&dopt=Abstract

[glbiochem]

Peptide Aldehyde is very hard to make. We met the same problem.

[Pawel35]

I am making peptide aldehydes using Novabiochem resins (they have with attached Leu - H-Leu-H NovaSyn TG Resin Cat# 04-12-3720). Cleavage is simple using TFA:TIS:H2O (95:2.5:2.5) mixture.
Then I am doing HPLC purification on C18 column (80% Acetonitryle/Water + 0.1% TFA and Water + 0.1 % TFA). From my experience I can say that yields are usually low.

By using this specific resin from Novabiochem yields are higher, than when I was using Weinreb resin and then Reductive cleavage.

[AplaGen]

Reaching >95% by only optimizing the purification is a difficult and expensive task. Do you know the impurities?

If yes: you should think about optimizing the synthesis, e.g. using capping procedures which modify the retention times of the unwanted side-products. That is the way we usually reach >95% when needed.

Andreas